This invention relates to a seal assembly for establishing a fluid-tight seal between two relatively movable members, one of which may be an inner rod or shaft. More specifically, the invention relates to a seal assembly in which the sealing element is in the form of a ring made of elastomeric material such as, for example, an O-ring.
Typically, the inner peripheral surface of the sealing ring sealingly engages the shaft member while the outer peripheral surface of the sealing ring seals against an outer member which encircles the shaft. When pressure is applied to the high pressure end of the sealing ring, the ring is compressed and its low pressure end is pressed axially against a radially extending retainer which backs the low pressure end of the sealing ring.
In conventional sealing assemblies, fluid is trapped in the vicinity of the outer peripheral surface of the low pressure end of the sealing ring and tends to be compressed when pressure is applied to the high pressure end of the ring to press the ring axially against the retainer. The pressure exerted radially by the trapped fluid forces the inner peripheral surface of the sealing ring radially into tight gripping engagement with the shaft. When there is relative movement between the shaft and the seal, the high radial loads caused by the trapped fluid result in friction and heat which increases the wear and reduces the service life of the sealing ring.